1. Field of the Invention
The present invention relates to heat sensitive recording paper, i.e. thermographic recording paper, on which recording can be carried out by means of a thermal head, thermal pen, or the like, and to base paper from which said recording paper is made up.
2. Description of the Prior Art
Sheets of heat sensitive recording paper were originally applied to printers for medical purposes and instrumentation purposes and have been recently used increasingly in the fields of facsimiles and terminal image output devices. This has been attended upon a need for heat sensitive recording paper which, at high speeds of recording, exhibits higher sensitivity and provides higher quality images than does the conventional. To meet this need, a measure hitherto taken is optimizing materials for heat sensitive recording layers or optimizing the way of dispersing these materials. However, effects adequate to satisfy said need cannot be obtained with this measure alone. Hence it is practiced, as an approach through physical properties of paper, to elevate the surface smoothness of heat sensitive recording paper, thereby improving the conformity, in other words, the ability to contact intimately, of the paper with the thermal head.
Various calender treatments of heat sensitive recording paper, that is, paper coated with a heat sensitive layer, are practiced to improve the conformity of the recording paper. However, the surface smoothing of heat sensitive recording paper by calendering alone cannot sufficiently improve the conformity of the paper at the time of printing, wherein the back side of said paper is rolled out with a platen roll and is then pressed to the thermal head, and hence this type of treatment cannot provide as high sensitivity and dot reproducibility as expected.
As regards the base paper, much satisfactory paper is not obtained even when the surface smoothness is improved by calendering under proper conditions.